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PubMed1991

Comparative studies on the vector capacity of the different stages of Amblyomma variegatum Fabricius and Hyalomma rufipes Koch for Congo virus, after intracoelomic inoculation.

Groups of nymphs and adults of Hyalomma rufipes and larvae, nymphs and adults of Amblyomma variegatum were infected by intracoelomic inoculation with Congo virus at concentrations of 10(3.5)LD50 (Group A), 10(1.5)LD50 (Group B) and 10(0.5)LD50 (Group C). The infection rates for the different groups were: Groups A, 92-100% for all stages of ticks, except for adult H. rufipes which had 87%; Group B, 56.8, 68.1 and 50.7% for larvae, nymphs and adults of A. variegatum, respectively, and 96.3 and 84.4% for nymphs and adults of H. rufipes, respectively; Group C, 0% for larvae, nymphs and adults of A. variegatum and 8 and 1.7%, respectively, for nymphs and adult adult of H. rufipes. The 1-5% infection threshold was 10(0.5)LD50 for nymphs of H. rufipes and a dose greater than this for all the other stages of the two species of ticks. The 50% infection threshold was 10(1.5)LD50 for larvae and adults of A. variegatum, but less than 10(1.5)LD50 for nymphs of A. variegatum and nymphs and adults of H. rufipes. Peak virus titres obtained for H. rufipes were 10(6.0) for Group A and B nymphs and 10(3.0) for Group A and B adults, and 10(1.0) each for Group C nymphs and adults. For A. variegatum, the peak titres for Groups A, B and C were, respectively, 10(1.0), 10(0.8), and 0 for nymphs and 10(1.5), 10(0.6) and 0 for adults. Sera from 100% (24/24) of rabbits used to feed adult H. rufipes and from 65% (31/48) used to feed nymphs and adult A. variegatum were positive for compliment fixation antibody to Congo virus at a titre of 1:8 from Days 15-35 postattachment of ticks. Viremia in rabbit was detected in 12.5% (3/25) of rabbits used to feed adult H. rufipes.

Animals↗
PubMed2004

Influence of the blood meal source on the biology of Meccus longipennis (Hemiptera: Reduviidae) under laboratory conditions.

Influence of the blood meal source on life cycle, mortality, and fecundity of 2 cohorts of recently colonized Mexican Meccus longipennis, fed on hens (H-cohort) or rats (R-cohort) were evaluated in laboratory conditions. One hundred twelve nymphs (56%) (H-cohort) and 102 nymphs (51%) (R-cohort), completed the cycle. The average time from Nymph I to adult was 209+/-41 days (H-cohort) and 239+/-28 days (R-cohort), taking an average of 1.8 (H-cohort) and 1.9 (R-cohort) blood meals per nymphal stage (range 1-6). The average span in days for each stage from the H-cohort was 20.8 for Nymph I, 24.5 for Nymph II, 38.8 for Nymph III, 56.1 for Nymph IV, and 72.5 for Nymph V, and it was 20.2 for Nymph I, 23.1 for Nymph II, 43.2 for Nymph III, 68.8 for Nymph IV, and 75.4 for Nymph V from the R-cohort. The mortality percentage was 44% (H-cohort) and 49% (R-cohort). The average number of eggs laid per female in a 9-month period was 484.1 (range 351.1-847.8) in the H-cohort, whereas the average number of eggs was 442.3 (range 288.5-720.5) in the R-cohort. No significant differences (P > 0.05) were recorded among cohorts fed on the studied blood meal sources, different from most previously studied Triatominae species, perhaps due to a high degree of association of M. longipennis with chickens and hens as much as with mammals under natural conditions on human dwellings.

Animals↗
PubMed2004

The roles of birds, lizards, and rodents as hosts for the western black-legged tick Ixodes pacificus.

We compared the infestation by ixodid ticks of lizards, rodents, and birds collected simultaneously within areas representing common habitat types in Mendocino County, CA. Lizards were infested only by Ixodes pacificus Cooley and Kohls, birds by I. pacificus and Haemaphysalis leporispalustris (Packard), and rodents by I. pacificus, I. spinipalpis Hadwen and Nuttall, I. woodi Bishopp, Dermacentor occidentalis Marx, and D. variabilis (Say). Infestation by I. pacificus larvae and nymphs of lizards (Sceloporus occidentalis Baird and Girard; Elgaria spp.) and western gray squirrels (Sciurus griseus Ord) (means of 9-35 larvae and 5-6 nymphs per animal) was several times greater than for Neotoma fuscipes Baird woodrats, Peromyscus spp. mice, and birds (means of 0.9-3.5 larvae and 0-0.3 nymphs). Overall, Borrelia-refractory lizards accounted for 84% of I. pacificus larvae and 91% of nymphs collected from animals in dense woodlands. Bird species frequently utilizing tick-questing substrates such as leaf litter (guild I birds) were more heavily infested by I. pacificus subadults (5.2 larvae and 1.0 nymphs per bird) than guild IV birds with minimal perceived contact with tick-questing substrates (0.08 larvae and 0.06 nymphs per bird). Notably, guild I birds carried similar larval loads and at least 20-fold higher nymphal loads relative to woodrats and mice. Only guild IV birds carried as few I. pacificus nymphs as did these rodents. The ratios of larvae to nymphs suggest that, relative to birds, lizards, and squirrels (infested by 1.3-6.0 larvae per nymph), nocturnally active ground-dwelling rodents such as woodrats and mice are underutilized by the nymphal stage (69 to >100 larvae per nymph). The western gray squirrel and guild I-II birds (e.g., the dark-eyed junco, Junco hyemalis [L.]) were the only potential reservoirs of Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt, and Brenner (the causative agent of Lyme disease in North America) that were frequently infested with both I. pacificus larvae and nymphs and commonly utilized dense woodland habitats.

Animals↗
PubMed2005

A collection of ticks (Ixodidae) from wild birds in Uruguay.

Thirty nine wild birds from seven families (Alcedinidae, Emberizidae, Furnariidae, Parulidae, Trochilidae, Turdidae and Tyrannidae) were caught from 4 to 7 of February, 2004 at Rincón da Vassoura (31 degrees 15' S 56 degrees 03' W) Department of Tacuarembó, Uruguay. Ninety one nymphs and forty one larvae of Ixodidae were recovered from them. The majority of ticks were conventionally identified but 16S mitochondrial rDNA sequences were obtained for larvae and nymphs of Amblyomma with uncertain specific status to be compared with sequences of species from this genus. The 16S rDNA of Haemaphysalis juxtakochi Cooley was also obtained. Most ticks, 1 nymph of Amblyomma longirostre (Koch), 5 larvae of Amblyomma aureolatum (Pallas) and 3 nymphs of Amblyomma spp., 10 nymphs and 71 larvae of H. juxtakochi, 23 nymphs and 12 larvae of Ixodes pararicinus Keirans and Clifford, were found on the 5 Turdus albicollis Vieillot and 6 Turdus rufiventris Vieillot (Turdidae) caught. One nymph of A. longirostre and 2 nymphs of I. pararicinus were collected from the only Syndactyla rufosuperciliata (Lafresnaye) (Furnariidae) captured; 1 larva of I. pararicinus was collected on one of two Basileuterus leucoblepharus (Vieillot) (Parulidae) trapped and 1 nymph of A. longirostre was found on one of nine Elaenia parvirostris Pelzeln (Tyrannidae) captured. All these findings constitute new host records with the exception of I. pararicinus on S. rufosuperciliata, and stress the importance of Turdus as hosts for I. pararicinus, H. juxtakochi and A. aureolatum. Nymphs of H. juxtakochi and Amblyomma spp. were also found on man and vegetation.

Animals↗
PubMed1994

Marking Dermacentor variabilis (Acari: Ixodidae) with rubidium.

Studies were conducted to determine the feasibility of marking Dermacentor variabilis (Say) with the alkali metal rubidium (Rb) by feeding larvae on mice that were injected with rubidium chloride (RbCl). Newly molted nymphs that fed as larvae for 2 to 5 d on RbCl-injected mice contained approximately 660 parts per billion (ppb) of Rb, whereas nymphs that had fed for 6 to 10 d as larvae on RbCl-injected mice contained 419 ppb of Rb. Nymphs that fed as larvae on control mice contained approximately 9 ppb. There was no host-specific difference in Rb concentration among nymphs obtained from four RbCl-injected mice. Rb-marked nymphs did not show reduced survival as compared with unmarked nymphs when survival was monitored for 8 wk. Rb concentrations in unfed nymphs remained close to 600 ppb for 3 wk, then declined to approximately 380 ppb for 5 wk. Rb concentrations in experimental nymphs remained significantly higher than in control nymphs for 8 wk. Adults that molted from Rb-marked nymphs that had fed on control mice did not contain elevated levels of Rb. This marking method has considerable potential for aiding in population ecology studies of ticks under natural conditions because ticks can be marked via their hosts and the mark will be retained for the duration of the life stage without passing the mark to subsequent stages.

Animals↗
PubMed1996

Nymphal sexual dimorphism in the sheep tick Ixodes ricinus (Acari: Ixodidae).

Unfed nymphs of Ixodes ricinus (L.) can be divided into two morphological groups according to the length of idiosoma, scutum, hypostome and palpal segment III, and the number of dorsal alloscutal setae. Specimens of greater body dimensions and more numerous dorsal alloscutal setae moulted predominantly into females. The frequency of different nymphal length categories in field-collected ticks followed a normal distribution. The length of unfed nymphs correlates well with the length (r = 0.7248 +/- 0.0711, P < 0.001) and weight (r = 0.6519 +/- 0.0782, P < 0.001) of engorged nymphs, however, it varies in ticks of different origin. In field-collected ticks, freshly engorged female nymphs were 2.30-2.94 mm long, male nymphs 2.14-2.46 mm long. Feeding period (P < 0.05) and premoulting period (P < 0.001) were significantly longer in female nymphs both in field-collected and laboratory-derived I. ricinus. The engorgement weight was found to be the best criterion for differentiation of male and female nymphs of ixodid ticks. In field-collected nymphs engorged on BALB/c mice, 98.6% of females moulted from nymphs weighting more than 3.60 mg, while in laboratory-derived ticks, 98.4% of females emerged from nymphs of 3.42 mg body mass or more.

Animals↗
PubMed1996

Presence of Ixodiphagus hookeri (Hymenoptera: Encyrtidae) in two Connecticut populations of Ixodes scapularis (Acari: Ixodidae).

Two Connecticut populations of the black-legged tick, Ixodes scapularis (Say), the vector of Lyme disease spirochetes, Borrelia bugrdorferi sensu stricto Johnson, Schmid, Hyde, Steigerwalt & Brenner, in the northeastern United States, are parasitized by the encyrtid wasp Ixodiphagus hookeri (Howard), formerly Hunterellus hookeri. The wasp was first detected in ticks from a forested site in Bridgeport in 1992. I. hookeri was reared from 18.6% of 148 host-seeking I. scapularis nymphs. In 1993 and 1994, this wasp was found to parasitize 26.0% of 192 engorged nymphs from Bridgeport and 21.8% of 101 nymphs from the Bluff Point Coastal Preserve in Groton. Each parasitized nymph produced an average of 6-8 wasps (range, 3-16) with a female to male sex ratio of 1.9-1. Both study sites are wooded, geographically isolated tracts (Bridgeport, 176 ha and Bluff Point, 326 ha) with high densities (51-72/km2) of white-tailed deer, Odocoileus virginianus (Zimmerman), and superabundant tick populations similar to that of Prudence Island, RI, where I. hookeri also has been reported. We found that I. hookeri emerged from 16.3% of 399 engorged nymphs and 13.7% of 1,081 engorged nymphs collected as unfed ticks from Prudence Island in 1990 and 1991, respectively. No wasps were obtained from nymphs collected in Stamford (n = 38) or Old Lyme, CT (n = 241). A high proportion (23.1% of 39) of engorged nymphs obtained from Bridgeport deer produced I. hookeri. However, only 2 nymphs (6.7%) recovered from white-footed mice, Peromyscus leucopus (Rafinesque), at Bridgeport were parasitized by the wasp. None of the engorged larvae recovered from deer or mice and fed as nymphs in the laboratory produced I. hookeri (n = 26 from deer and n = 384 from mice). The presence of this wasp in I. scapularis at these 2 insular-like sites on the Connecticut mainland supports the observation that high tick densities are required for the establishment and maintenance of I. hookeri and that the potential role of this wasp in the biological control of I. scapularis is limited.

Animals↗
PubMed1996

Effect of 25-azacholestane on Argas (Argas) hermanni (Ixodoidea:Argasidae).

Unfed and fed nymphal Argas hermanni Audouin were treated topically with 1, 5, 10, 15, and 20 micrograms of 25-azacholestane. The azasteroid did not inhibit feeding but had a dose-related lethal effect on unfed nymphs. Generally, it had little effect on nymphs treated after feeding. The 10-micrograms dose reduced the premolting period of nymphs treated before feeding. Some adults emerging from the 5- to 20-micrograms dosage groups that had been treated before feeding failed to shed their exuvia and others also had deformed legs. Greater numbers of adult females emerged from nymphs treated before feeding. The preoviposition period was almost the same in control females and of female mates, with males emerging from treated nymphs. Females from nymphs treated before feeding have a prolonged preoviposition period. Fecundity was reduced when males were treated with 10-20 micrograms as unfed nymphs. Egg hatch was reduced for females treated with 15 and 20 micrograms as fed nymphs, females treated with 5 and 10 micrograms as unfed nymphs, and as progeny of males treated with 10 micrograms as unfed nymphs. Results suggest possible interference with juvenile hormone titer in treated ticks.

Animals↗
PubMed1998

Central processing of aggregation pheromones in solitary and gregarious desert locusts, Schistocerca gregaria.

In the desert locust, Schistocerca gregaria, a number of behaviorally active aggregation pheromone components have been identified from adult male S. gregaria, and from third, fourth and fifth instar nymphs. Adult females seem not to produce aggregation pheromones. Adult males and females, but not nymphs respond to the adult male-produced mixture, whereas only nymphs respond to the binary nymph-produced mixture with aggregation behavior. We studied the structure and function of antennal lobe interneurons, responding to single aggregation pheromone components and adult- and nymph-specific mixtures. Neurons in adult males and females and in first instar nymphs of S. gregaria in the solitary and the gregarious phase were investigated. Projection neurons responded with different degrees of specificity to all behaviorally active aggregation pheromone components. Component-specific, blend-specific and generalist neurons were found in adults and first instar nymphs in both phases. Antennal lobe neurons were slightly more sensitive in solitary than in gregarious locusts. In gregarious adult males and females more neurons responded to the adult male mix than to any of the single components. In gregarious first instar nymphs most neurons responded to the adult male mix and the major component but also nymph mix specific neurons were found. The behavior of adults and nymphs is thus partially reflected by the response characteristics of antennal lobe projection neurons.

Animal Communication↗
PubMed2000

Relationship between weights of the engorged nymphal stage and resultant sexes in Ixodes scapularis and Dermacentor variabilis (Acari: Ixodidae) ticks.

The relationship between weights of the nymphal stage and their resultant sexes in Ixodes scapularis Say and Dermacentor variabilis (Say) was examined under laboratory conditions. Nymphs were fed to repletion on laboratory white mice, weighed individually, and held until they molted. Fully engorged I. scapularis nymphs that subsequently molted to females weighed between 3.8 and 6.4 mg (n = 64). Those nymphs that molted to males weighed between 2.0 and 3.2 mg (n = 57). Body weights of engorged nymphs that became females were significantly greater than those of nymphs that became males (P < 0.05). Similarly, the range of body weights of engorged D. variabilis nymphs that subsequently became females was 9.1-15.1 mg (n = 32), whereas those nymphs that molted to males weighed between 3.9 and 13.0 mg (n = 39). Body weights of engorged nymphs that became females were significantly greater than those of nymphs that became males (P < 0.05). This suggests that nymphs of both species that become females presumably imbibe more blood than those that became males.

Animals↗